1. Field of the Invention
The present invention relates to novel naphthopyran-type compounds that have, in particular, photochromic properties. The invention also relates to the use of these photochromic compounds in ophthalmic articles (goggles, lenses and eye-shields, for example). The invention particularly relates to naphthopyrans having an oxygen-containing saturated heterocyclic group fused to the naphthalene ring. These naphthopyrans have two intense absorption bands in the visible light range, and are particularly suitable for use in photochromic articles, such as eyeglass lenses, which have a brown or driver activated color.
2. Background of the Art
Photochromism generally concerns the ability of a compound to reversibly change color under different light conditions. One particular type of photochromic phenomenon concerns the reversible change in color of a compound from an original color to a different color when the compound is exposed to a source of ultraviolet radiation, such as solar radiation or light radiated from a mercury or xenon lamp. The photochromic compound fades to the original color within a period of time after the photochromic compound is isolated from the ultraviolet radiation, such as by placing the compound in a dark room.
Photochromic compounds find applications in various fields, such as for the manufacture of ophthalmic lenses, contact lenses, solar protection glasses, goggles, sun screens, filters, camera optics, photographic apparatus optics or other optical devices and observation devices, glazing, decorative objects, currency elements and even for information storage by optical inscription (coding). For example, photochromic compounds, such as naphthopyrans, are incorporated into plastic ophthalmic lenses to effect color changes in the lenses when the lenses are exposed to particular lighting conditions. Additionally, different photochromic compounds may be blended together to create a color effect that is different from respective color effects of the individual photochromic compounds. As an example, a first photochromic compound that turns orange or red when activated by light and a second photochromic compound that turns blue when activated by light may be blended together to form a photochromic mixture that produces a shade of gray when activated by light.
Amongst the numerous photochromic compounds described in the prior art, naphthopyrans and larger ring systems derived from them received the most intensive investigations due to their suitable properties (fatigue, fading rate, color, temperature dependence) for use in eyeglass lenses. The simplest naphthopyran photochromic compounds are represented by the formula below:

Attempts were made to achieve improvements by using different substituents at various positions, especially on the naphthalene core. The improvements include proper fading rate, desired color, better fatigue, etc. One of the important improvements is for a naphthopyran to provide a blended color hue. As aforementioned, to give eyeglass lenses a neutral gray or brown color, it may necessitate the use of at least two photochromic compounds of different colors, i.e., two separate compounds having distinct maximal absorption wavelengths in the visible region of the electromagnetic spectrum. However, the use of combinations of photochromic compounds imposes other requirements on both the individual photochromic compounds and the groups of photochromic compounds. In particular, the coloration and discoloration kinetics of the (two or more) combined active photochromic compounds must be essentially identical. The same applies for their stability with time, and also for their compatibility with a single plastic or inorganic support.
It is thus highly desirable to obtain photochromic compounds that have a blended color hue provided by two or more distinct absorption bands in the visible region. With such photochromic compounds it is possible to use only one compound for the desired color (e.g., gray or brown), or at least to require minimum amount of complementary color compound.
U.S. Pat. No. 5,645,767 discloses photochromic indeno[2,1-f]naphtho[1,2-b]pyrans having a blue/gray activated color. A blue/gray color will be perceived when there is a major absorption of visible light in the 580–620 nm range (Band B thereafter referring to the longer wavelengths) coupled with a minor absorption in the 420–500 nm range (Band A thereafter referring to the shorter wavelengths).
U.S. Pat. No. 6,096,246 (incorporated by reference) describes naphtho[1,2-b]pyrans having alkoxy groups as substituents at the 7- and 9-positions of the naphthopyran ring. The activated forms of these compounds exhibit two intense absorption bands in the visible light range. It is reported that the optical density of Band A in some cases is higher than the optical density of Band B, but in the majority of cases Band A is of lower optical density than Band B.
U.S. Pat. No. 6,146,554 (incorporated by reference) discloses photochromic indeno[2,1-f]naphtho[1,2-b]pyrans having a green activated color. A greenish color will be perceived when there is a major absorption of visible light in the 580–620 nm range coupled with a major absorption of roughly equal intensity in the 400–480 nm range. U.S. Pat. No. 6,248,264 (incorporated by reference) describes naphtho[1,2-b]pyrans having amino functional groups as substituents at the 7- or 9-positions of the naphthopyran ring. These compounds are disclosed as exhibiting a brown or red/brown activated color. A red/brown color will be perceived when there is a major absorption of visible light in the 420–500 nm range coupled with a minor absorption in the 520–560 nm range.
U.S. Pat. Nos. 6,296,785 and 6,348,6043 (incorporated by reference) disclose indeno[2,1-f]naphtho[1,2-b]pyrans and naphtho[1,2-b]pyrans, respectively, having two adjacent moderate to strong electron donor substituents at the 6 and 7 positions of indeno[2,1-f]naphtho[1,2-b]pyrans and the 8 and 9 positions of naphtho[1,2-b]pyrans. The activated forms of these compounds exhibit two intense absorption bands in the visible light range. In the majority of cases Band A (420–500 nm) is of stronger optical density than Band B (480–620 nm) making them suitable for use in photochromic articles having a brown activated color.
U.S. Pat. No. 6,353,102 (incorporated by reference) describes naphtho[1,2-b]pyrans having carbonyl functional groups as substituents at the 6-position of the naphthopyran ring. These compounds are disclosed as also exhibiting two absorption bands in the visible light range. The relative intensity of the two bands depends on other substituents on the ring.
From the above description, it is apparent that photochromic compounds having two absorption bands can be obtained by selecting certain substituents at the naphthopyran ring, especially at the 6 to 9 positions of the naphtho portion. Although some prior art references teach how to select substituents, it seems that such prior art references are incomplete and do not achieve the formulative results of the present invention.
Therefore, it is an object of this invention to provide novel series of photochromic compounds that exhibit two intense absorption bands in the visible range wherein the relative intensity between Band A and Band B is greater than unity. These photochromic compounds will be especially useful in making brown or driver (red-brown) photochromic articles such as eyeglass lenses with a single compound or minimum use of a complementary color compound.
All publications and patents referred to in this application are hereby incorporated by reference.